critical9.1

CVE-2026-40575

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers.

Impact

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-auth-route` is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session. Impacted users are deployments that run oauth2-proxy with `--reverse-proxy` enabled and configure at least one `--skip-auth-regex` or `--skip-auth-route` rule. This issue is patched in `v7.15.2`. Some workarounds are available for those who cannot upgrade immediately. Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level; explicitly overwrite `X-Forwarded-Uri` with the actual request URI before forwarding requests to OAuth2 Proxy; restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy; and/or remove or narrow `--skip-auth-regex` / `--skip-auth-route` rules where possible. For nginx-based deployments, ensure `X-Forwarded-Uri` is set by nginx and not passed through from the client.

Affected packages

Ecosystem	Package	Affected	Fixed in
go	`github.com/oauth2-proxy/oauth2-proxy/v7`	>= 7.5.0, < 7.15.2	7.15.2

Affected products

Vendor	Product	Affected versions
Oauth2 Proxy Project	Oauth2 Proxy	from 7.5.0 before 7.15.2

Weakness classification

CWE-290

Impact

Affected packages

Affected products

Weakness classification

References